kit

commit df8e73dd8c00a501a3b593bb97730af95321f574
parent 3fd5286ad48412a72fd8adde095d9d1784622ef0
Author: Ryan Sepassi <rsepassi@gmail.com>
Date:   Mon, 25 May 2026 15:07:10 -0700

Fix C backend bitfield base addresses

Diffstat:
M
src/arch/c_target/emit.c
 | 
46
+++++++++++++++++++++++++++++++++++++++++++++-

1 file changed, 45 insertions(+), 1 deletion(-)
diff --git a/src/arch/c_target/emit.c b/src/arch/c_target/emit.c
@@ -2736,13 +2736,57 @@ static const char* c_bf_storage_type(u32 size) {
   }
 }
 
+/* Spell an address expression for a backend-addressable lvalue operand.
+ * Unlike c_emit_operand, this never reads the object value; it materializes
+ * the address of the local/global/indirect storage itself. */
+static void c_emit_lvalue_addr_expr_raw(CTarget* t, Operand addr) {
+  char buf[24];
+  SrcLoc loc = t->cur_fn ? t->cur_fn->loc : (SrcLoc){0, 0, 0};
+  switch (addr.kind) {
+    case OPK_LOCAL:
+      cbuf_putc(&t->body, '&');
+      c_slot_name(addr.v.frame_slot, buf, sizeof buf);
+      cbuf_puts(&t->body, buf);
+      return;
+    case OPK_GLOBAL: {
+      obj_sym_mark_referenced(t->obj, addr.v.global.sym);
+      const char* nm = c_sym_name(t, addr.v.global.sym);
+      cbuf_puts(&t->body, "((char*)&");
+      cbuf_puts(&t->body, nm);
+      if (addr.v.global.addend != 0) {
+        cbuf_puts(&t->body, " + ");
+        cbuf_put_i64(&t->body, addr.v.global.addend);
+      }
+      cbuf_putc(&t->body, ')');
+      return;
+    }
+    case OPK_INDIRECT: {
+      CAddrMode m = c_addr_mode(addr);
+      if ((u32)m.base >= t->reg_cap || !t->reg_declared[m.base]) {
+        compiler_panic(t->c, loc,
+                       "C target: bitfield on undeclared base reg v%u",
+                       (unsigned)m.base);
+      }
+      cbuf_putc(&t->body, '(');
+      c_emit_indirect_addr_expr(t, m);
+      cbuf_putc(&t->body, ')');
+      return;
+    }
+    default:
+      compiler_panic(t->c, loc,
+                     "C target: bitfield address on operand kind %d not "
+                     "supported",
+                     (int)addr.kind);
+  }
+}
+
 /* Spell `*(uintN_t*)((char*)addr + bf.storage_offset)` into the body. */
 static void c_bf_storage_lvalue(CTarget* t, Operand addr, BitFieldAccess bf,
                                 const char* storage_ty) {
   cbuf_puts(&t->body, "(*(");
   cbuf_puts(&t->body, storage_ty);
   cbuf_puts(&t->body, "*)((char*)");
-  c_emit_operand(t, addr);
+  c_emit_lvalue_addr_expr_raw(t, addr);
   if (bf.storage_offset != 0) {
     cbuf_puts(&t->body, " + ");
     cbuf_put_u64(&t->body, (u64)bf.storage_offset);